Reflection: It is the process which light is bounced back. In reflection the angle of incidence is equal to the angle of reflection.

Properties of an image in a plane mirror :

* The image is as far behind the mirror as the object is in front.

* The image is the same size as the object.

* The image is virtual – that is , it cannot be produced on a screen appear to be interchanged.

Refraction: It is the process which bends the light away from the normal bend it.

Luminious Object: These are the object that can emit light on its own and doesnot requires to be see. Eg : sun.

Non-luminious object: These are the object that cannot emit light on its own and doesnot requires to be see. Eg : moon.

Laws of reflection :

1. i) The angle of incidence is equal to the angle of reflection.
2. ii) The incident ray , the reflected ray and the normal all lie in the same length.

Incident ray: The light from the source to the mirror or the object is called incident ray.

Reflected ray: The light from the object or mirror to the eye is called reflected ray.

Normal: It is the imaginary line perpendicular to the object / mirror at the point of incidence.

Note : The incident angle and the reflected angle are the angles between the incident ray and the reflected ray , with the normal respectively.

Reasons for refraction :

1. i) Due to internal friction in the material medium the velocity of light is reduced and hence bends to

achieve a reduced speed.

Note: A medium is a material such as glass or water through which light can travel.

Note: When light passes through the normal among media no refraction takes place.

Laws of refraction :

1. i) The incident ray , the refracted ray and the normal all lie in the normal.
2. ii) The snells law – The ratio of the sin of the incident angle to the sin of refracted angle are constant

between a particular media.

Refractive Index: It is the ratio of the sin of incidence to the sin of refraction.

* Refractive index of glass – 1.33

* Refractive index of water – 1.50

The Equation of refractive Index: Sin i / Sin r = Constant.

* Refraction is the bending or change of direction of light due to the change in material medium.

Total Internal Reflection: When light travels from denser to the right medium. It refracts away from the normal , with a partial reflection. When an angle of incidents , is increased the refracted ray moves further away from the normal of a certain angle of refraction of 90°. This incident angle is called critical angle.

Critical Angle: For light travelling from denser to lighter medium the incident angle for which the refracted angle is 90°.

* If the incident angle is further increased , the light , instead of biasing refracted is now reflected into medium and follows the laws of reflection. This phenomenoansis known as total internal reflection. Eg : Glowing of eyes of cats and dogs at low light in the dark , sparkling of diamond and glass prism.

Total internal reflection : During travelling the rays of light from more denser medium to less denser medium , when the light strikes the surface at an angle of incidence greater than critical angle , no light can pass through and return the previous medium.

Critical angle : When the rays of light travels from more denser medium to less denser medium , for which the angle of refraction becomes 90° is called critical angle.

Optical Fibre : They are very thin , flexible glass rods , used for carrying light . It is used in endoscope , ii) It is used in telecommunication system , iii) It is used in prismatic periscope.

Properties of images:

* Images created with rays of light actually passing through them is known as real image. On the other hand , in virtual images rays of light do not pass through them.

* Real image can be formed on the screen , but virtual image cannot be formed on screen.

Regular reflection :  This time light strict a very smooth surface to continue to regular direction.

Luminious object :   eg – sun , star , bulb , television screen , laser , florescent tube.

* Non-luminious object reflect light from other source.

* Light travels through space at 3 × 10⁸ m/s.